In recent years the role of statewide freighting forecasting models has been expanded to much finer levels of analysis than regional or even county levels, those being the most disaggregate spatial levels for which public freight data sources are typically available. In partnership with other state agencies and Metropolitan Planning Organizations (MPOs), the California Department of Transportation (Caltrans) is currently developing a California Statewide Freight Forecasting Model (CSFFM). A critical challenge is to provide a framework for organic integration between the CSFFM and a finer spatial level such as that in the new California Statewide Travel Demand Model (CSTDM) to meet Caltrans and MPO needs. However, factoring methods are currently largely used for disaggregating freight demand. Such methods cannot adequately capture the complex structure and behavior of freight movements, advances in logistics, information technology, and relocating infrastructure at the MPO level. One advantage of the CSFFM, modal path-based OD representation, cannot be fully utilized by MPOs because factoring methods tend to break the chains of modal path-based information in the conversion to trip-based information. This research initially sought to explore and develop truck tour-based models for disaggregating CSFFM from an aggregate Freight Analysis Zone (FAZ) level to the more disaggregate Traffic Analysis Zone (TAZ) level in CSTDM, by using truck GPS data from the American Transportation Research Institute (ATRI). Expected results included new and improved insights into the spatial and temporal operations of trucks at the urban and MPO level, contribution to the statewide-related component of urban freight modeling, and an evaluation of traffic and environmental impacts of state-level policies and air pollution mitigation strategies. However, after detailed investigation of the ATRI GPS data it was concluded that several problems with the data made it inadequate for disaggregating a CSFFM truck matrix for about 200 FAZs to the CSTDM 5000 TAZ level. Therefore, a new approach was developed. It involved estimation of a direct demand model at the CSFFM FAZ level using as inputs only independent variables readily available at CSTDM’s level of aggregation and, as dependent variables, the final truck matrices estimated by CSFFM. The model will then be applied to CSTDM’s zoning system with the resulting estimates being appropriately scaled to match the input CSFFM matrix (with one scaling factor per cell of the CSFFM truck trip table). This procedure has the following desired properties

This research constructs a statewide freight forecasting model for California, as the follow-up to an initial preparation phase conducted for the California Department of Transportation (Caltrans). In that initial phase, the scope of the model was defined, the modeling methodology and data needs determined, and a preliminary software platform selected. The objective of this phase is to implement the statewide freight forecasting model so that it can be used to evaluate policy scenarios and integrate with local and state models. The final deliverables of this project include a core model framework that can address the basic immediate needs of the state and local agencies, to be completed within a 2-year time frame. The core model is designed as a state of the art model to address the highest priority needs of the state, for which a state of the practice four-step commodity flow model would be inadequate. It consists of several primary modules: a commodity generation module, a commodity distribution module built on a destination-based logit allocation model called fractional split distribution, and a logit-based joint mode-route choice model. Factors are used to convert annual commodity flows to daily or peak period flows, and to convert commodities to commercial vehicles which are then assigned along the routes determined from the joint mode-route choice model. The handling of transshipments in the core model will be based on either Cube Cargo's TLN module or a network assignment approach that incorporates transfer costs that is available in TransCAD.